Rotary air valves for wind type musical instruments are useful items which direct the air flow from the mouthpiece through either a main air passage or a slide loop.
Of particular interest are four U.S. Patents issued to Orla E. Thayer, U.S. Pat. Nos. 4,112,806; 4,213,371; 4,299,156; and 4,469,002. Each of these patents discloses the use of a rotary air valve positioned along the air flow path of a slide trombone. In each case, the rotary air valve serves to direct the air through either the main air conduit or to divert air into a slide loop and thence back into the main air conduit and to the instrument bell.
In each of the Thayer patents identified, the rotary air valve is positioned in the air flow path with the valve apertures and conduits positioned generally parallel to the axis of rotation of the valve rotor. This type of construction and valve orientation resulted in the formation of sharply inclined, diverging air passages which negatively affected the tonal quality of the sound produced. Also, these valves required relatively complex mechanical linkages between the actuating lever and the rotor which slowed the shifting of the rotor between its extreme positions. This flaw affected both the tonal quality of the sound and detracted from the playability of the instrument.
Also, the rotary valves disclosed in the Thayer patents teach the use of two air flow conduits through the rotor. The first air conduit is positioned along the axis of rotation of the rotor to allow the first conduit air outlet to remain in constant communication with the main conduit. In this fashion air flowing through the rotor first conduit must turn both axially and radially through the rotor before it reaches the main bore. This negatively affects tonal quality of the horn.